AC unit trips breaker occasionally on restart when extremely hot out. Will run fine for hours after breaker is set back, but will occasionally trip again during hottest part of day when system is cycling often. I have replaced the thermostat, condenser fan motor, capacitors, contactor, breaker, and added a hard start kit. I have also cleaned the coils, cleaned inside of unit, and removed all shrubs near the unit to allow unobstructed airflow. Any suggestions? I’m thinking high head pressure but don't know how to check. My thermostate has a 5 min. delay, but it might not be enough time. I was also going to get an AMP reader to try to identify what is pulling the amps, but I never know when it is going to trip. HELP! This has been a frustrating and expensive problem so far. Any suggestions are greatly appreciated

Check the actual circuit breaker... it may be weak. With the main breaker off at the main breaker box in the house(not the disconnect) check all electrical connections from the house to the condenser unit for a secure bond. Note any wires that look like they have darkened due to heat. Double check the gauge of the wiring with the run amps for the condenser.

What kind of hard start kit did you buy? Is it specifically meant for your condenser?

Unfortunately yes. This unit worked fine for years until now without recharging so I'm not sure how it would've gotten overcharged. Coils are now clean and put a nice sturdy p-trap on there to replace the BS garden hose that was attached

sounds like your compresor might be short cycling like say a 24v wire that opens and closes real fast causing the contactor to chatter. Evidence of this would be a heavily pitted contactor even after a short time. The other thing could be a short in the compressor that only opens when its hot. The statement about overcharge could be correct also. Sounds like the tech is making some money though. You may need to upgrade.

My contactor was heavily pitted when he pulled it out. The 24v wire you mentioned that opens and closes quickly - are you talking about its connection with the contactor? I've sat outside with my amp meeter around different legs at startup, but have not found anything to pull above normal. But again, I have difficulty recreating the trip. I should also mention that when it does trip it is not immediately on startup. It will run for 8-10 seconds before it trips. Your thoughts are VERY much appreciated.

sounds like a problem with the dropout voltage on the start relay. as mentioned before, if the hard start kit is not the right size for your system, there can be trouble. the relay is supposed to hold the capacitor out of the loop for the duration of the cycle. if it is re-introduced into the circuit, an overload can occur.

the technician should have cleaned your condenser and evaporator if needed. he should have also been able to detect all these other issues. if it is an intermitent problem, there is a possibility the compressor is going south. however, i agree that it's more likely the technician is not being thorough. a technician that replaces all parts and doesn't clean coils raises a flag.

also, just to be sure, you said you replaced the breaker several times. hopefully you did not go up in size in any of these changes. the breaker is sized to protect the wire. an oversized breaker can increase the risk of a fire. it's a common mistake to install a bigger one to keep it from tripping.